In 2013, a federal judge ruled that Arpaio's practice of using traffic patrol officers to check immigration status targeted Latinos. The 85-year-old also used armed volunteers to patrol malls and go after suspected immigrants has run for Senate seat in the past but lost to Democrat Paul Penzone.

Arpaio announced his candidacy in a Tweet this afternoon:

I am running for the U.S. Senate from the Great State of Arizona, for one unwavering reason: to support the agenda and policies of President Donald Trump in his mission to Make America Great Again. https://t.co/ANppBdDOtp

"I am running for the U.S. Senate from the Great State of Arizona, for one unwavering reason: to support the agenda and policies of President Donald Trump in his mission to Make America Great Again," said Arpaio in a statement.